Good thinking. But if you buy entry level, and aren't impressed at all, you may never want another pair, and I can say with surety that some of the mid-tier to upper end DO sound better IMO (than their entry level pairs). The reason I kept the HE400S is because, while they were considered entry level, they sound better than some of the higher end ones (to my ears). If you HAVE the money to spend on them, I would maybe suggest skipping to the Deva (new model), or the Sundara (well loved mid-tier). But I digress, because I have NOT heard the HE400SE, so they might sound better to you..... It is a conundrum for sure. LOL
If the HE400SE are anything like the HE400S or HE400i, then the sound you will be getting is more akin to the HD600/650, than the 598 from all that I have read. Keep in mind that back when the HE400S and HE400i (not 2020 version) were about $300 and $400 so things might have changed. Hifiman is terrible with their model numbers, and it is hard to tell what is an upgrade, or side grade, etc...